Stem and envelope for electron discharge devices



Nov. 15, 1960 A. J. STOECKERT 2,960,620

STEM AND ENVELOPE FOR ELECTRON DISCHARGE DEVICES Filed Sept. 8, 1959 INVENTOR. ALVIN J. STUEEKERT w Zm My;

Azmwsr STEM AND ENVELOPE FOR ELECTRON DISCHARGE DEVICES Alvin .li. Stoeckert, Cedar Grove, N.J., assignor to Radio Corporation of America, a corporation of Delaware Filed Sept. 8, 1959, Ser. No. 838,483

9 Claims. (Cl. 313-617) My invention relates to electron discharge devices and more particularly to an improved stem and envelope construction for facilitating manufacture of such devices.

In one form of electron discharge device, the electrode assembly is supported on a stem comprising a header member of ceramic material of flat disk-like or wafer form and the electrode lead-in and support wires which extend through and are sealed in the header. The stem and electrode assembly are mounted within a tubular envelope having a base portion of larger transverse dimension than the rest of the envelope. The envelope is provided with a transverse shoulder between the base portion and the other portion of the envelope. The header member rests on the shoulder during the bakeout, exhaust and sealing steps during manufacturing operations, as will be described below. The header member is provided with a metallized peripheral surface which is brazed to the inside wall of the base portion of the envelope after bakeout and exhaust to seal the envelope vacuum tight.

In the manufacture of a tube of the kind described, the electrodes are first secured to the lead wires and the header to form a complete electrode mount assembly. This mount assembly is then inserted in inverted position into the envelope which is also in inverted position during exhaust and sealing, with the header received loosely within the base portion of the envelope and with the inner surface of the header resting on the shoulder between the base portion and the elongated tubular portion. A ring of. brazing material is then placed within the base portion and rests above the periphery of the header member and next to the inner wall of the base member. This assembly is then placed within an evacuated exhaust and sealing apparatus. The entire assembly is then subjected to a temperature sufficiently high to outgas the electrodes and at the same time activate the cathode. The gases escape from the interior of the envelope between the shoulder of .theenvelope and the header resting thereon into the exhaust chamber of the exhaust and sealing apparatus. After thisheating step the tube is subjected to higher temperature for causing the brazing ring to melt and to braze the peripheral surface of the header member to the inner wall of the base member.

Because of the fact that the flat inner surface of the header member adjacent the periphery thereof contacts the fiat surface of the shoulder over a comparatively large area, the passage for the gases generated during bakeout is restricted. This makes it difficult for the gases to readily escape from inside of the envelope thus slowing down bakeout and exhaust operations. As a result rapid mass production of a tube using this type of header and envelope construction is diflicult. 7

It is therefore an object of my new invention to provide a stern and envelope construction which will provide an optimum free exhaust path between the envelope and header member during thebakeout and exhaust, steps in the manufacture of electron discharge, devices of the type described;

tent O Z,%,6Z0 Patented Nov. 15,1960.

An electron discharge device using my invention includes a tubular envelope having atone end a base portion of larger transverse section than the rest. of the envelope. In order to provide as much space as possible between the header and theenvelope for a free exhaust path during exhaust, in accordance with my invention, I provide the envelope intermediate the base portion and the remainder of the'envelope with an inwardly flared or tapered portion, tapered away from the base portion. In order to support the header member during exhaust and sealing, in a position normal to the longitudinal axis of the envelope, I provide the envelope in the tapered portion thereof with a plurality of inwardly directed projections, the projections having supporting surfaces lying in a common plane normal to the longitudinal axis of the tube. As a result, While the header member is properly supported within the base portion of the envelope during bakeout and exhaust, a minimum of sur-- face contact exists between the header and the inner wall of the envelope. This arrangement provides a free exhaust pathvbetween the flat surface of the header and the inner wall of the envelope. Since there is a loose fit between the peripheral surface of the header member' and the inner wall of the base portion of theenvelope,

the gases during exhaust may easily escape from the envelope.

Referring to the drawings:

Fig.- 1 is a side elevation partially in section showing the construction of a prior art type of electron discharge device;

Fig. 2 is a bottom plan View of Figure 1. showing the base portion and the relationship of the header member with the base portion of the envelope;

Fig. 3 is a partial side elevation partially in section showing the construction of the header memberand envelope made according to my invention; and

Fig. 4 is a bottom plan view of Fig. 3.

Fig. 1 illustrates one form of electron discharge device of the prior art using a fiat disc header. The header member 10 which may be a ceramic disk has extending,

therethrough and sealed therein the lead-in conductors and support wires 11, 11 for supporting and providing electrical connection to the electrodes mounted thereon. These electrodes include the cathode 12, the grid 13 and the anode 14 which are supported respectively upon the flange supports 15, 16 and 17. These flanges are supported in turn on the inner ends of the lead-in and support conductors 11, 11.

The envelope includes the elongated portion 20 and the base portion 22. The base portion 22 is of a larger diameter than the elongated portion 20 and supports the header member 10 on a transverse shoulder 21. It will be noted that there is considerable area of contact between the inner flat surface of the header member 10 and the shoulder 21. The header, which is provided with a metallized periphery, is brazed at 10 vacuum tight to the inner wall of the base portion 22.

In baking out, exhausting and sealing the assembly, the envelope, header member and electrode assembly are passed through an evacuated exhaust and sealing apparatus and in an inverted vertical position as shown in Fig. l.

The entire assembly is first subjected to a temperature sufficiently high to bake out the electrodes and to activate the cathode. Since the header member is merely resting upon the shoulder 21 of the envelope, the gases can escape from the interior of the envelope to the exterior thereof into the exhaust apparatus. However, since there is a large area of contact between the flat surface of the header and the shoulder, the passageway for-the gases is restricted; As a result, much time is necessary for exhausting the envelope. Mass produc- 1 tion is therefore retarded. After the tube has been baked out, the temperature in the exhaust and sealing apparatus is raised to increase the temperature of the brazing ring 23 to cause it to melt and seal the peripheral surface of the header member to inner wall of base portion 22 of the envelope with a vacuum tight seal.

Figs. 3 and 4 illustrate the stem and envelope construction incorporating my invention.

An envelope having a base portion 31 is provided intermediate thebase portion and the remainder of the envelope, which may be elongated, with a flared portion 32 having at spaced intervals the inwardly projected supporting elements 33 of which there may be a plurality, three being shown, for supporting the header member 34 brazed to the inner wall of the base portion at 34'. These elements are formed in the flared portion of the envelope. The electrode elements shown supported by header member 34 correspond to those shown in Fig. 1.

With the construction shown very little of the surface of the header member 34 is in contact with the inwardly projecting elements 33. Thus, a nearly completely free exhaust ,space- 35 is provided between the inner face of header member 34 and the tapered or flared portion 32 of the envelope. Prior to brazing, of course, the space occupied by brazing material 34 is free with only the brazing ring 36 (shown in dotted line) resting lightly on the periphery of the header member and closely adjacent the inner wall of the base portion of the envelope. The free exhaust space between the header and the envelope permits the gases to easily leak ofl during exhaust into the evacuted space within the exhaust and sealing apparatus.

What is claimed is:

l. Anelectron discharge device including a stem comprising a flat header member having a peripheral surface normal to the flat surfaces of said header member and an electrode assembly supported on one of said flat surfaces, and an envelopewithin which said stem and said elec-' trode assembly are received, said envelope having a tubular portion and, at one end, a base portion within which said header member is received for closing said base portion, the intermediate portion of said envelope between the tubular portion and said base portion being formed to provide a space between said intermediate portion and said header member, said space providing a free exhaust path between said intermediate portion and said header member during bakeout and exhaust, said envelope being provided with a plurality of inwardly projecting supporting elements extending from said base portion to said tubular portion and having surfaces lying in a plane normal to the longitudinal axis of said envelope, said surfaces of said elements engaging the flat surface of said header member from which said electrode assembly is supported.

2. An electron discharge device including a stem comprising a flat header member having a peripheral surface normal to the flat surfaces of said header mem-- ber-and an electrode assembly supported by said header member, an envelope receiving said stem and said electrode assembly, said envelope having a tubular portion and, at one end, a base portion receiving said header member, said header member being brazed to the inner wall of said base portion, the portion of said envelope between the tubular portion and said base portion being provided with a plurality of inwardly projecting elements having surfaces lying in a plane normal to the longitudinal axis of said envelope, said inwardly projecting elements engaging a flat surface of said header member whereby only a small area of contact exists between said flat surface of said header member and said elements for providing a free exhaust path between said flat surface and said envelope during bakeout and exhaust prior to sealing.

3. An electron discharge device including a stern comprising a header member and an electrode assembly supported on said header member, an envelope receiving said stem and said electrode assembly, said envelope having a tubular portion and, at one end, a base portion receiving said header member, said header member being sealed to the inner wall of said base portion at its periphery, the intermediate portion of said envelope between the tubular portion and said base portion and the inner surface of said header member being provided with mutually contacting portions lying in a plane normal to the longitudinal axis of said envelope and having only a small area of contact between said intermediate portion of said envelope and the inner surface of said header member whereby a free exhaust path is provided between said inner surface of said header member and the inside wall of said envelope during bakeout and exhaust,

4. An electron discharge device including a stem comprising a flat header member having a peripheral surface normal to the flat surfaces of said header member, and anenvelope, said envelope having a tubular portion and a base portion. at one end for receiving said header member, said base portion having a larger transverse dimension than said tubular portion, the portion of said envelope between the elongated portion and said base portion being flared inwardly and toward the end of the tubular portion remote from said base portion, and a plurality of inwardly projecting supporting elements extending from said base portion to said tubular portion and having supporting surfaces lying in a plane normal to the longitudinal axis of said envelope, said supporting surfaces engaging one flat surface of said header member, said flared portion during exhaust and bakeout of said electron discharge device providing a free exhaust path between said envelope and said header member.

5. An electron discharge device including a stem comprising a header member having a flat surface on one side thereof and a peripheral surface normal to the flat surface, electrode means supported on said header and an envelope within which said stem and said electrode means are received, said envelope having an elongated tubular portion and a tubular base portion at one end within which said header member is received, said base portion having a larger transverse dimension than said tubular portion, the portion of said envelope between the elongated portion and said base portion being flared inwardly and away from Said base portion, said flared portion being provided with a plurality of inwardly projecting supporting elements having supporting surfaces lying in a plane normal to the longitudinal axis of said envelope, said supporting surfaces engaging the flat surface of said header member, said flared portion during exhaust and bakeout of said electron discharge device providing a free exhaust path between said flared portion and said header member.

6. An electron discharge device including a stem comprising a flat header member having a peripheral surface normal .to the flat surfaces of said header member and electrode means supported from one flat surface thereof, and an envelope receiving said stem and said electrode means, said envelope having an elongated tubular portion and a tubular base portion at one end for receiving said header member and closing said base portion, said base portion having a larger transverse dimension than said tubular portion, the portion of said envelope between the elongated portion and said base portion being tapered inwardly and away from said base portion,

. said flared portion being provided with a plurality of inwardly projecting supporting shoulders having flat supporting surfaces lying in a plane normal to the longitudinal axis of said envelope, said supporting surfaces engaging a flat surface of said header member, said tapered portion during exhaust and bakeout of said electron discharge device providing a free exhaust path be tween said envelope and said header member.

7. An electron discharge device including a stem comprising a flat insulating disk-like member having a peripheral surface normal to the flat surfaces of said disklike member and supporting electrode means thereon, and an envelope within which said stem and said electrode means are received, said envelope having an elongated tubular cylindrical portion and at one end a tubular cylindrical base portion within which said disk-like mem her is received, the peripheral surface of said header member being sealed to the inner wall of said base portion, said base portion having a larger diameter than said tubular portion, the portion of said envelope between the elongated portion and said base portion being tapered inwardly and away from said base portion, said tapered portion being provided with a plurality of inwardly projecting supporting elements having supporting surfaces lying in a plane normal to the longitudinal axis of said envelope for engaging one flat surface of said disk, said tapered portion during exhaust and bakeout of said electron discharge device providing a free exhaust path between said envelope and said disk-like member.

8. An electron discharge device including a stem comprising a header member having a peripheral surface, and an envelope receiving said stem, said envelope having a tubular portion and a base portion at one end, said header being received within said base portion and having a peripheral surface sealed to the inner wall of said base portion, said base portion having a larger transverse dimension than said tubular portion, the portion of said envelope between the tubular portion and said base portion being flared inwardly and away from said base portion, said flared portion being provided with a plurality of inwardly projecting supporting elements having supporting surfaces engaging one surface of said header member, said flared portion during exhaust and bakeout of said electron discharge device providing a free exhaust path between said envelope and said header member.

9. An electron discharge device including a closure member having a peripheral surface and an envelope, said envelope having an elongated tubular portion and at one end a portion having a larger transverse dimension than said elongated tubular portion and within which said closure member is received, the peripheral surface of said closure member being sealed vacuum tight to the inner wall of the envelope portion of larger transverse dimension, the portion of said envelope between the elongated tubular portion and said portion at said one end being tapered inwardly away from said one end, said envelope being provided with a plurality of inwardly projecting supporting elements extending from said portion of larger transverse dimension to said elongated tubular portion and having surfaces engaging a surface of said closure member other than said peripheral surface, said tapered portion providing a space between said envelope and said closure member whereby a free exhaust path between said envelope and said closure member is provided during bakeout and exhaust operations during manufacture of said electron discharge device.

References Cited in the file of this patent UNITED STATES PATENTS 2,014,809 Kuhle Sept. 17, 1935 2,078,892 McCullough Apr. 27, 1937 2,476,387 Roovers July 19, 1949 2,731,578 McCullough Jan. 17, 1956 

